The present invention relates to a screw compressor, especially for use as a super-charger for an internal combustion engine.
Such a screw compressor comprises a housing, having a barrel section and two end sections, enclosing a working space provided with inlet and outlet ports and formed by two intersecting bores, and a pair of intermeshing rotors mounted in the housing, each rotor being provided with helical lands and intervening grooves.
A screw compressor according to the invention is an improvement to earlier used super-chargers, e.g. turbo chargers which give a poor efficiency especially at low speed of the engine. A compressor according to the invention may suitably be driven by the crank shaft of the engine through a belt drive, which means that independent of the number of revolutions, the compressor can always deliver a volume of air enough to fill the engine and having a pressure higher than atmospheric pressure. Such feeding of pressurized air to the engine results in a higher power delivered.
In a screw compressor it is essential that the barrel section and the end sections of the housing in mounted position has acceptable rigidity for the intermeshing rotors to act properly. Earlier known compressor housings have been produced from east iron, which results in a rather heavy compressor partly due to the high density of iron, and partly due to relatively thick walls. Such housing further requires a considerable mount of work to cut the housing to exact dimensions (measure deviation 0.03 to 0.05 mm). Screw compressor housings have also been east from aluminium. In order to obtain the necessary stability the barrel section and one end section are cast as one unit. This means complicated bottom hole manufacture and thick walls. All those compressors are thus relatively heavy and bulky and are thus unsuitable for mounting on the side of the engine.
The aim of the present invention is to avoid the disadvantages mentioned above and to obtain a number of advantages in comparison with the earlier known screw rotor super-chargers.